In a well$-$mixed batch reactor, for an elementary reaction, the following

concentration$-$time data are being obtained. The smallest squares for this reaction are

using the method

Time, t $[$min$]50100200300$

CA$($t$)[$M$]0\mathrm{.}007870\mathrm{.}006490\mathrm{.}004810\mathrm{.}00380$

a$)$ Of the reaction $1.$ mi $2.$ find out which degree it is$.$ The validity of your result

please explain

b$)$ Calculate the initial CA$0$ concentration of the reaction.